Twelve volunteers, (four males), age range 21 to 33 years (age mean (SD), 27.2 (3.3) years) participated in the study. None had a history of major illnesses, and on a routine medical examination they were all found to be of normal health. All twelve subjects resided for approximately three months prior to testing at the place where the tests were held. This allowed their diet and schedule (e.g., meal times and time of waking up or sleeping) to be kept constant on the day before testing and on the two days of assessment. The subjects had all been practicing different yoga techniques (asanas and pranayamas, excluding SAV) for approximately ninety minutes every day, during the three months prior to the study. The subjects did not practice the yoga techniques during the days of the study in order to reduce the chance of the short-term effects of these practices modifying the effects of the pranayama practice (i.e., SAV) that was studied.
Design of the study : Assessments were made on two separate days as soon as the subjects woke up in the morning, between 4:15 AM and 5:30 AM. Assessments were taken, followed by the test period (45 minutes), at the end of which assessments were repeated. On day one the test period involved practicing surya anuloma viloma pranayama (SAV) for 45 minutes. This involves breathing exclusively through the right nostril. On day 2, during the 45-minute test period, subjects were asked to breathe normally. This was called the NB session. Half the subjects (selected on a random basis) were given SAV sessions first, followed by NB sessions on the next day. The six remaining subjects had NB sessions on day one and SAV sessions the next day.
Assessment : The sequence of assessment was the same for the recordings made before and after the test periods of both SAV and NB. The sequence was as follows: Subjects were asked to rest for 5 minutes, seated at ease. Oxygen consumption (OC) was recorded for 5 minutes using the closed circuit Benedict-Roth apparatus. Recordings were made almost immediately after waking up in the morning. This was followed by a 10-minute recording of polygraph data viz. heart rate through EKG, skin resistance, respiration, and digit pulse volume as detailed below. The blood pressure (BP) was recorded once at the end of the 10-minute recording. This sequence was repeated at the end of the test period.
Oxygen consumption (OC) was recorded for 5 minutes using the closed circuit Benedict- Roth apparatus. Recordings were made almost immediately after waking up in the morning. Polygraphic recordings were made using a 10 channel polygraph (Model 10, Polyrite, Recorders and Medicare, Chandigarh, India). The EKG was recorded using standard limb lead 1 configuration. The skin resistance (SR) was recorded using specially contoured metal electrodes smeared with electrode jelly (Medicon, Madras, India) and placed in contact with the volar surfaces of the distal phalanges of the index and middle fingers of the left hand. A fixed current of 1OuA was passed between the electrodes. Respiration was recorded using a volumetric pressure transducer fixed around the trunk about 8 cm below the lower costal margin as the subject sat erect. A photo-plethysmograph was placed on the volar surface of the distal phalanx of the left thumb to record the digit pulse volume (DPV).
The blood pressure was recorded with a standard mercury sphygmomanometer, auscultating over the right brachial artery. The diastolic pressure was noted as the reading at which the Korotkoff sounds appeared muffled. Recordings were made of the (subjective) feelings the subjects experienced at the end of both sessions. Subjects were shown how to monitor their nasal airflow using a method described earlier (Klein, Pilon, Prossner & Shannahoff- Khalsa, 1986), by breathing on a glass slide and noting which patch of mist was smaller and/or faded more quickly.
Data acquisition and analyses : The OC was calculated in ml/min and converted to ml/min Standard Temperature and Pressure Dry (STPD), according to the accepted procedure (Report of the International Union of Physiological Sciences Commission on Teaching Physiology, 1991). Heart rate (HR) in beats per minute (bpm) was obtained by continuously counting the QRS complexes in successive
60 second periods. The skin resistance (SR) trace was sampled every 30 seconds. The amplitude of the digit pulse volume (DPV) was sampled from the peak of pulse wave at 30-second intervals and converted to millivolts (mV) (Roy & Steptoe, 1991).
The data were analyzed using the 2-factor ANOVA, the multiple comparison Tukey test, and the paired t test. The ANOVA was used to determine whether there was a significant difference between SAV and NB sessions (Factor A), the readings before the test period compared to the readings obtained after it (Factor B), and interaction between Factors (A X B). The multiple comparison Tukey test was used to check the least significant difference between different pairs of means. As a second level analysis, the t test for paired data was used to compare the initial and final data of SAV and NB sessions separately.
Pranayama (SAV) and normal breathing (NB) : During both surya anulorna viloma pranayama (SAV) and normal breathing (NB), subjects sat either in padmasana (lotus posture) or sukhasana (sitting cross-legged at ease), with their eyes closed. Surya anuloma viloma pranayama (SAV) involves breathing exclusively through the right nostril, while the left nostril is kept occluded with gentle pressure from the ring and little finger of the right hand (Nagendra, Mohan & Shriram, 1988). During normal breathing (NB) there was no voluntary manipulation of the nostrils.
During the three months prior to the study, the subjects practiced the following yoga techniques:
1. Asanas: ardha cakrasana/ lateral arc posture (left and right side), ardha cakrasana/ half-wheel posture, padahastasana/ forward-bend posture, ardha matsyendrasana/ half-twist posture, ustrasana/ camel posture, pascimotanasana/ posterior stretching, bhujangasana/ serpent posture,Salabhasana/ locust Posture, dhanurasana/ bow Posture, sarvangasana/ shoulder-stand, matsyasana / fish Posture, and Savasana/ corpse Posture.
2. Pranayamas: sectional breathing, nadisuddhi (purification of subtle perception paths), ujjayi (hissing pranayama), and bhrahmari (bee sounding pranayama).